High voltage generators of the above type, also known as charge pumps, generally comprise a series of voltage multipliers consisting of capacitors and diodes (or transistors connected as diodes) that multiply by a given factor an input voltage that is typically the supply voltage of the integrated circuit. A high voltage generator of the above kind is described in a paper by J. F. Dickson published on 3 Jun. 1976 in IEEE Journal Of Solid State Circuits, Vol. SC. 11, No.3, pages 374–378, entitled “On-chip high voltage generation in NMOS integrated circuits using an improved voltage multiplier circuit”, for example. The disclosure of that paper is hereby incorporated by reference into the present description.
Thus if the charge pump comprises 14 stages, for example, it is possible to generate a voltage up to ten times a given supply voltage, for example 2 volts, at the input of the charge pump.
However, this kind of high voltage generator has a number of drawbacks, as it requires a relatively large circuit structure, for which space must be reserved on the integrated circuit.
Moreover, integrating this kind of integrated circuit into portable objects such as telephones, cards or even laptop computers does not lead to optimum battery life conditions in respect of the requirements of the object itself. One major concern in this field is reducing power consumption and using the lowest possible circuit supply voltage, in particular to extend the service life of the power supply means.
An object of the present invention is to alleviate the drawbacks of the prior art referred to above and in particular to provide a high voltage generator of the generic type indicated that either generates a high voltage using a charge pump comprising a much smaller number of multiplier stages than was necessary in the prior art or reduces power consumption by using a lower circuit supply voltage.